Meaning of tilde in Linux bash not home directory

Question

First off  I know that    is the home directory  CDing to   or    takes me to the home directory   However  cd  X takes me to a special place  where X seems to be anything   In bash  if I hit  cd    and hit tab  it shows a bunch of possible  X options like  mail and  postgres and  ssh   Going to those folders and doing a pwd shows me that these folders are not in the home directory  they re all over the place   They are not aliases  I ve checked   They re not env  variables  or else they d require a     What is setting these links  and where can I find where these are being set

User · Answer

It s a Bash feature called  quot tilde expansion quot   It s a function of the shell  not the OS  You ll get different behavior with csh  for example  To answer your question about where the information comes from  your home directory comes from the variable  HOME  no matter what you store there   while other user s homes are retrieved real-time using getpwent    This function is usually controlled by NSS  so by default values are pulled out of  etc passwd  though it can be configured to retrieve the information using any source desired  such as NIS  LDAP or an SQL database  Tilde expansion is more than home directory lookup  Here s a summary                  HOME  fred           freds home dir                   PWD        your current working directory   -              OLDPWD     your previous directory   1              dirs  1   2              dirs  2   -1             dirs -1   dirs and  1   -1  etc   are used in conjunction with pushd and popd

User · Answer

On my machine  because of the way I have things set up  doing   cd                  work1 jleffler cd  jleffler        u jleffler   The first pays attention to the value of environment variable  HOME  I deliberately set my  HOME to a local file system instead of an NFS-mounted file system   The second reads from the password file  approximately  NIS complicates things a bit  and finds that the password file says my home directory is  u jleffler and changes to that directory   The annoying stuff is that most software behaves as above  and the POSIX specification for the shell requires this behaviour    I use some software  and I don t have much choice about using it  that treats the information from the password file as the current value of  HOME  which is wrong   Applying this to the question - as others have pointed out   cd  x  goes to the home directory of user  x   and more generally  whenever tilde expansion is done   x means the home directory of user  x   and it is an error if user  x  does not exist      It might be worth mentioning that   cd  -         Change to previous directory   OLDPWD  cd            Change to current directory   PWD    I can t immediately find a use for       unless you do some weird stuff with moving symlinks in the path leading to the current directory   You can also do   cd -   That means the same as  -

User · Answer

If you re using autofs then the expansion might actually be coming from  etc auto home  or similar for your distro    For example  my  etc auto master looks like    home2 auto home --timeout 60   and  etc auto home looks like   mgalgs -rw noquota intr space  space mgalgs

User · Answer

Those are users  Check your  etc passwd   cd  username takes you to that user s home directory

User · Answer

Tilde expansion in Bash   http   bash-hackers org wiki doku php syntax expansion tilde

User · Answer

It s possible you re seeing OpenDirectory ActiveDirectory LDAP users  automounted  into your home directory   In  nix    will resolve to your home directory   Likewise  X will resolve to  user X    Similar to automount for directories  OpenDirectory ActiveDirectory LDAP is used in larger corporate environments to automount user directories   These users may be actual people or they can be machine accounts created to provide various features   If you type  Tab you ll see a list of the users on your machine

User · Answer

Those are the home directories of the users  Try cd   your username   for example

User · Answer

Are they the home directories of users in  etc passwd   Services like postgres  sendmail  apache  etc   create system users that have home directories just like normal users

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